Unit 2: Nutritional Requirements of the Preterm Infant

Vitamin E is the term given to a group of eight naturally occurring compounds that share similar characteristics and biological activities. Alpha-tocopherol is the isomer most commonly found and also the most active (Greer 2005). Acting as an antioxidant, vitamin E protects cell membranes from oxidative stress (it prevents free radical propagation in plasma and membranes lipoproteins) (Traber & Stevens 2011). For the developing fetus, vitamin E is critical for the retina, neurodevelopment, and skeletal muscle (Leaf & Lansdowne 2014).

The vitamin E content of the fetus increases proportionally to the accumulation of fat during mainly the third trimester of gestation. Moreover, vitamin E has a limited placental transfer rate. Therefore, premature infants are usually vitamin E deficient at birth (Leaf & Lansdowne 2014).

In the premature infant, measuring vitamin E can be challenging, since serum levels normally do not correspond to tissue concentration. Lipoproteins in plasma transport tocopherol and its tissue deliverance is dependent on lipid and lipo-protein metabolism (Traber & Stevens 2011). Thus, vitamin E deficiency is considered when a serum tocopherol/total lipid ratio is lower than 0.8 mg/g (Leaf & Lansdowne 2014).

Clinical vitamin E deficiency in preterm infants is characterized by edema, thrombocytosis and hemolytic anemia. Onset of symptoms occurs around 6 to 8 weeks of age (Brion et al. 2003). Toxicity is rare; however concentrations above 35 mg/l have been associated with necrotizing enterocolitis and sepsis (Brion et al. 2003). A Cochrane review published in 2003 (Brion et al. 2003) aimed to assess the effects of vitamin E supplementation in preterm infants. Although vitamin E supplementation reduced the risk of severe retinopathy and blindness in VLBW infants and the risk in of intracranial hemorrhage in normal weight preterm infants, it increased the risk of sepsis in both groups. They therefore suggested that high doses of intravenous vitamin E supplementation resulting in  tocopherol levels higher than 3.5 mg/dl should be avoided.

A recent RCT in ELBW infants assessed the effects of a single oral dose of vitamin E (50 IU/kg). The single dose was able to raise tocopherol levels at 24 hours above the critical concentration of 0.5 mg/dl in most but not all infants. Additional studies are warranted to try to find a dosage that would avoid insufficiency for all infants without causing deleterious collateral effects (Bell et al. 2013).